Solid Phase Extraction (SPE) is an exhaustive sample preparation technique where a sample is cleaned and the target analyte(s) are pre-concentrated using sorbent chemistry, primarily via a coating on the surface of silica particles that accomplishes the quantitative recovery of one or more target analytes that are contained in simple to extremely complex sample matrices. When the sample matrix is complex, containing particulates, proteins, lipids, debris, or other structures, one or more time consuming sample matrix clean-up steps, such as filtration, centrifugation, or protein precipitation, are often required, which can result in significant loss of analyte. Typically, small silica particles are used to support the coating of sorbent materials. The coated silica particles are packed in a sorbent bed having the geometric format of, for example, a disc, cartridge, or cylinder. The sorbent bed can exert enough resistance to flow of an aqueous solution containing the target analytes that the imposition of a pressure differential is required for the extraction process.
Surface-bonded hybrid organic-inorganic polymer coatings and monolithic beds are popular sorbents for use in analytical microextraction. These systems display high chemical stability and offer a diverse array of extracting phases for solvent-free/solvent-minimized analytical sample preparation. The availability of a wide variety of sol-gel precursors and sol-gel active organic polymers allows facile synthesis of advanced material systems with unique selectivity, enhanced extraction sensitivity and high thermal, mechanical and solvent stability. These sol-gel derived hybrid organic-inorganic advanced material systems have been shown to be effective in solvent-free/solvent-minimized sample preparation for a wide variety of analytes with biological, environmental, clinical, toxicological, food, pharmaceutical, bio-analytical, and forensic significance.
Sol-gel technology for the preparation of solid phase microextraction (SPME) sorbents has solved many limitations of conventional coatings. Sol-gel coatings are chemically bonded to many substrates, such as silica, when the gel is formed from the sol solution in the presence of the substrate. Because of the wide variety of possible sol components, sol-gel technology allows the synthesis of a large number of sorbents for SPME with large surface area, unique selectivity, and high thermal and solvent stability. Sol-gel monolithic beds are capable of achieving very high sample pre-concentration factors. The versatility of sol-gel technology allows the creation of surface-bonded sorbent coatings on unbreakable fiber materials (e.g., Ni—Ti, stainless steel, titanium, and copper) and also on substrates of different geometrical formats such as planar SPME (PSPME), and membrane SPME (MSPME). Sol-gel technology is adaptable to forming multi-component materials that have customized surface morphologies, selectivities and affinities of the sorbent. A wide variety of sol-gel silica, titania, zirconia, alumina, and germania-based precursors are commercially available. Additionally, a wide range of sol-gel reactive organic ligands are available to design hybrid organic-inorganic sol-gel coatings that can be used to target a particular analyte or sample matrix with improved selectivity, sensitivity, extraction phase stability and performance.
There remains a strong need for microextraction devices that permit the acquisition of very low concentrations of analytes that are present in a wide range of environments. Most microextraction devices are suited to a particular type of environment, and are often poorly suited for other environments. For example, some microextraction devices are well suited to sample air or other gases while others are suited for extraction from water or other liquids. Few microextraction devices can be easily adapted for sampling a solid surface. In addition, the limitation inherent to the geometric configurations of microextraction devices (smaller substrate surface area in both fiber and in-tube format) does not allow using a high amount of sorbent materials for extraction. The physical immobilization of polymeric materials on the substrate surface in microextraction devices limits their exposure to high temperature for thermal desorption and to organic solvents for solvent mediated desorption. As a result, many compounds with high boiling points and high polarity are still beyond the reach of microextraction devices. Microextraction devices are not recommended to make direct contacts with the sample matrix when it contains a high volume of particulates, debris or other matrix interferences that may cause irreversible damage to the sorbent coating.
A sampling device that can permit a uniform sampling of a broad variety of samples easily and effectively in the field is desirable, where more than one analyte, for example, neutral polar, nonpolar, organic acids, organic bases, heavy metals, and organometallics analytes, can be readily collected simultaneously during sampling, but where the collected analytes can be separately analyzed. There is a need for a sampling kit that comprises one or more easy-to-use devices that allow the acquisition of samples rapidly, reliably, and consistently when carried out by a skilled technician or even by an untrained individual that can follow the instructions with the kit, to allow for a high level of assurance that the samples are truly indicative of the analytes of interest.